This invention relates to a catalytic composite for the conversion of hydrocarbons. Additionally, the invention relates to a process for the use of the catalyst. The catalyst of the present invention is particularly useful in the catalytic reforming of hydrocarbons boiling in the gasoline range to produce in high yield a high octane reformate suitable for blending gasolines of improved anti-knock properties.
Catalytic reforming to upgrade naphtha or low-boiling range hydrocarbons to higher octane gasoline has been practiced for many years using catalysts comprising platinum on a refractory support, such as alumina. In the 1960's a major advance was made in this area when it was discovered that, in reforming a low-sulfur content hydrocarbon feedstock, the use of a catalyst comprising platinum and rhenium on alumina provided greatly improved yield stability and a much lower fouling rate. See U.S. Pat. No. 3,415,737 to Kluksdahl.
Since that time, a number of other patents have issued in the area of catalytic reforming using platinum-rhenium catalysts. Some of these patents have been particularly focused on use of relatively high rhenium to platinum ratio catalysts, including the following: U.S. Pat. No. 4,356,081 to Gallagher, which discloses the use of catalysts having rhenium to platinum ratios of from about 1.08 up to as high as 17, rhenium contents from 0.362 to 0.875 weight percent and platinum contents from 0.05 to 0.344 weight percent; U.S. Pat. No. 4,425,222 to Swan, which discloses multi-stage reforming using forward reactors having a catalyst with rhenium to platinum ratio less than 1.2 a rearward reactor having a catalyst with a rhenium to platinum ratio greater than 1.5, and a swing reactor having some catalyst of each ratio.
Platinum-alumina reforming catalysts are often made by impregnating alumina with a platinum compound. For example, U.S. Pat. No. 3,617,519 discloses the preparation of a platinum-rhenium-alumina reforming catalyst wherein the platinum is impregnated into an alumina support by commingling the alumina support with an aqueous solution of chloroplatinic acid. Following the platinum impregnation, the impregnated carrier is typically dried and subjected to a conventional high temperature calcination or oxidation treatment.
U.S. Pat. No. 3,617,519 discloses that in most cases it is advantageous to adjust the concentration of the halogen component in the platinum-rhenium-alumina catalyst during the calcination step by injecting, into the air stream used therein, an aqueous solution of a suitable halogen-containing compound. U.S. Pat. No. 3,617,519 discloses that the halogen component can be added to the catalyst in various ways including adding the halogen during the impregnation through the utilization of a mixture of chloroplatinic acid and hydrogen chloride.
Typical calcination temperatures used in the preparation of the alumina support for reforming catalysts cover a wide range from about 800.degree. to 1300.degree. F., and frequently are 1100.degree. F. or lower.
"Rheniforming F" catalyst, containing about 0.3 weight percent Pt, and about 0.6 weight percent Rhenium on an extruded alumina carrier has been marketed by the assignee of the present invention.
Rheniforming F has been sold under license and successfully used commercially for many years. This catalyst is particularly described as the first stage catalyst of the catalyst system described in U.S. Pat. No. 4,764,267 to Chen et. al. Rheniforming F is an extruded catalyst, that is, it is substantially cylindrical in shape. The extruded Rheniforming F catalyst has a bulk density of about 0.6 cc/g and a particle density of about 1.00 cc/g. A typical tamped packed bulk density is about 0.65 cc/g.
It is typically believed the yield stability performance of Rheniforming type catalysts are due to the metals loading levels. However, in the notoriously unpredictable hydrocarbon catalysis art, a catalyst having improved yield stability and increased liquid volume yield is always much desired.